Age and stage based analysis of the population dynamics of beluga whales, Delphinapterus leucas, with particular reference to the northern Quebec population

• Main Author: Doidge, D. W. (David William)
• Format: Thesis
• Language: English
• Published: McGill University 1990
• Subjects: White whale > Hudson Bay; Arctic; Hudson Bay; Hudson; Beluga; Beluga*; Delphinapterus leucas; Monodon monoceros; narwhal*; White whale; Alaska
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74610

The vital rates of beluga, Delphinapterus leucas, harvested in northern Quebec are within the range reported by previous studies in Alaska and the Canadian and Soviet Arctic. Small sample size and inadequate estimates of survivorship rates prevent meaningful calculation of population growth rate. The pattern of changes in vital rates over the life cycle of beluga and analysis of errors associated with stage classification indicate that the demographic information in a 6 x 6 age-grouped Lefkovitch matrix is similar to that in a 38 x 38 age class Leslie matrix. A 3 stage, length-based model composed of newborns, juveniles and adults contains less demographic information than the larger matrices, but is superior to a juvenile/adult classification scheme. The 3 stage model applied to length frequency data from aerial photographic censuses should provide an alternate method of demographic analysis when harvests are small or absent. Colour is a poor criterion for stage classification. Sensitivity analysis of fecundity and survivorship indicates that survival of gray animals (older juveniles and early breeders) has the most influence on population growth rate. Changes in fecundity have little effect on growth rate. The high sensitivity of population growth rate to juvenile and early adult survival demonstrates that these estimates should be improved if more precise knowledge of beluga demography is required for management purposes. The age-length data used to evaluate errors associated with stage classification indicate that belugas in Hudson Bay are smaller than those elsewhere, but not to the large degree previously reported. Beluga in estuaries are represented by all size classes. Examination of the integumentary heat loss show beluga and narwhal, Monodon monoceros, to be equally insulated, but only belugas frequent warmer estuarine waters.